This invention relates to compositions for topical application to animal (this term as used herein includes both humans and lower animals) tissue, said compositions providing enhanced penetration of various pharmacologically active substances into or through such tissue.
The epidermal barrier to percutaneous absorption, i.e., the stratum corneum, is a nearly impermeable heterogeneous animal tissue of which keratin is a major component. This tissue is found in animal skin and mucosal tissue such as tongue, gingiva, esophagus, and vagina. A wide variety of pharmacologically active substances are desirably applied topically to this epithelial tissue for an essentially local effect achieved upon penetration into or through the stratum corneum. For example, compositions used in the treatment of a variety of dermatoses, including acne vulgaris, tinea versicolor, acne rosacea and other skin maladies associated with hyperplasia of the infected sebaceous gland, are desirably treated by topical medications. Likewise, eczema and eczema-like skin disorders caused by excessive cell proliferation are treated by topical application of ointments and salves. Localized inflammation which often accompanies arthritis and bursitis is treated by topical medications, as is common muscular "strain" caused by overexertion. Topical anesthetics are widely used in medicine and dentistry. The cosmetic efficacy of a variety of agents such as antiperspirants, rubifacients and emollients depends on the ability of the cosmetic agents to penetrate the epidermal barrier. Accordingly, it is seen that any means whereby the penetration of pharmacologically active agents through skin can be enhanced is of substantial interest.
It is known that various surface-active compounds improve the activity of pharmacologically active substances, apparently by enhancing the penetration of same through skin. For example, U.S. Pat. No. 3,326,768 discloses that the presence of a phosphine oxide surfactant in antiperspirant compositions containing anticholinergic compounds appears to increase activity by providing more efficient absorption of the active agents at the site of application. U.S. Pat. No. 3,527,864 discloses the use of alkyl sulfoxides to enhance the penetration of a variety of pharmacologically active agents through skin. The co-pending application of Warren I. Lyness and James Scala entitled "Compositions for Topical Application to Animal Tissue and Method of Enhancing Penetration Thereby", Ser. No. 230,040, filed Feb. 28, 1972, relates to the use of phosphine oxides to enhance the penetration of a variety of agents through skin.
Many surface-active compounds enhance the permeability of skin by actually damaging the barrier tissue. Indeed, the degree of penetration enhancement appears in some cases to be proportional to the extent of tissue damage. Certain organic solvents serve to enhance penetration of substances through the epidermal barrier. For example, dimethyl sulfoxide (DMSO) and homologous low molecular weight sulfoxides, when used in solvent concentrations, e.g., 50% or more, will enhance penetration of various substances; see U.S. Pat. No. 3,551,554. However, such compounds are systemically distributed in a very short time and can cause undesirable symptoms at these higher concentrations.
While the foregoing higher sulfoxides and phosphine oxides are suitable for enhancing skin penetration, improved compositions providing a greater degree of penetration and improved clinical efficacy are desirable. It is, therefore, an object of this invention to provide improved compositions for topical application to animal tissue and an improved method for enhancing the penetration of pharmacologically active substances through such tissue. It is a further object to provide a method of enhancing the penetration of pharmacologically active substances into or through animal tissue, especially skin, without damaging said tissue or causing adverse systemic effects. These and other objects are obtained herein as will be seen from the following disclosure.